1982 650 - xs/xj maxim conversion - frame difference

OK I know I am asking a strange question - I have a $50 1982 maxim 650 that has not run in about 10 years, can be made to run again and a decent bike to ride, but I want to make a wild chopper custom - whats the difference in the frames? converting down to a 2 cylinder would work or not? going to hardtail the back of course, and would like a chain cause of the stretch int eh rear frame... what about the backbone? different? basically if someone has pictures of a stock xj frame bare, and a stock xs frame bare..